1. Field of the Invention
The present invention relates to an alignment apparatus for substrates, particularly to an alignment apparatus for substrates preferable for positioning the substrates in a manufacturing or transferring apparatus of the substrates such as a semiconductor substrate, liquid crystal panel substrate, and mask substrate.
2. Description of the Related Art
In recent years, in a semiconductor manufacturing apparatus, there have been demands not only for further improvement in operation stability, productivity, and accuracy but also for flexible treatment of various types of product as well as one standard product. For example, in recent years, a mini-manufacturing line in which various types of product are manufactured in small quantities has been noted. In the background, one of the aims lies in that various types of product are handled by one manufacturing apparatus to reduce manufacturing costs.
In detail, as represented by an original plate mask substrate for exposure, liquid crystal panel, and plasma display, there has been a demand for a manufacturing apparatus which can handle substrates including a plurality of materials and outer shape standards. In this manufacturing apparatus, it is important to transfer the substrate to an accurate predetermined position regardless of the type of substrate, and it is necessary to dispose an alignment apparatus which meets this demand. Moreover, naturally, for yield improvement of substrate manufacturing, generation of waste or damage in a transfer or alignment operation needs to be avoided, and it is important to realize a mechanism in which dust is not generated in principle.
In a related-art alignment apparatus, because of simplicity of the mechanism, the substrate has heretofore been positioned or centered by an abutment method for general purposes, but the generation of waste or damage by contact of an abutment portion or frictional movement of the substrate has raised problems. Then, to solve the problem, a non-contact system centering apparatus or positioning transfer apparatus has been proposed. Examples of the apparatus are disclosed in Jpn. Pat. Appln. KOKAI Publication Nos. 11-106044 and 11-150172, but any of these is limited to a wafer having a predetermined size, and different sizes cannot be handled. Moreover, considering application of these known techniques to a rectangular substrate, not to the wafer, the substrate thickness varies, there are various types made of transparent or opaque materials, and therefore a combination of the above-described known arts cannot satisfy desired requirements.
The related art includes an example in which with various types of substrate thicknesses, a substrate mounting holder for exclusive use is used to transfer the substrate. In Jpn. Pat. Appln. KOKAI Publication No. 2000-182561, there is proposed a method of measuring the substrate thickness in an electron beam drawing apparatus. However, in this example, the apparatus configuration becomes complicated, and it is necessary to automatically transfer and align the substrate onto the holder. Moreover, for example, in a mask original plate for exposure, an opaque film, halftone film, photosensitive resist, and conductive thin film are formed, and in many cases it is difficult to sense the position of the substrate with optically predetermined accuracy and likelihood.
Particularly, as represented by notch detection of the wafer, in a notch detection method of emitting light from a substrate surface side, and receiving the light on a substrate back surface side to detect a light amount change, a detection error has been caused by an edge cut of a wafer peripheral portion of resist or an optical property or film thickness non-uniformity of film formation of an underlayer. Moreover, the film formed in the substrate surface is generally turned and formed also into substrate side surfaces. Therefore, when only a usual laser displacement sensor is used, it is difficult to sense the position with the predetermined accuracy. Furthermore, even when the presence/absence of the substrate is sensed by a threshold value of a reflection amount of laser beams, it has been difficult to accurately sense the substrate because of various film states described above.
In this manner, it has heretofore been difficult to perform accurate alignment regardless of the types of the substrates including a plurality of materials and outer shape standards or without being influenced by the film formed on the substrate surface or without causing dust generation or substrate damage or breakage. Moreover, in the substrate manufacturing apparatus, there has been a demand for realization of an alignment apparatus which can preferably be applied regardless of environment, such as the atmosphere and vacuum, and which is simple and inexpensive.